CFCs (chlorofluorocarbons) and HCFCs (hydrochlorofluorocarbons), which have been used as refrigerants for conventional refrigeration equipment, have become objects of regulations due to the problem of recent ozone layer depletion, and HFCs (hydrofluorocarbons) have come to be used as refrigerants instead of them. Of HFC refrigerants, for example, R134a is normally used as a refrigerant for automobile air conditioners. Furthermore, recently, use of unsaturated fluorinated hydrocarbon refrigerants such as HFO-1234yf has been suggested, of which ozone depletion potential (ODP) and global warming potential (GWP) are both very small and of which thermodynamic properties, which are measures of refrigerant performance, are equivalent to or greater than those of R134a.
For example, in Patent Literature 1, a refrigerating machine oil that contains a polyol ester composed of a polyhydric alcohol selected from pentaerythritol, trimethylolpropane, and neopentyl glycol and a fatty acid and predetermined additives, as a refrigerating machine oil for R134a, is disclosed. Alternatively, for example, in Patent Literature 2, a refrigerating machine oil that contains, as the main component, an ester of one or more selected from neopentyl glycol, trimethylolpropane, pentaerythritol, and dipentaerythritol and one or more selected from monovalent fatty acids having 7 to 9 carbon atoms, as a refrigerating machine oil for HFO-1234yf, is disclosed.